SCIENTIFIC OBSERVATION-RAILWAYS. 
53 
numerous ; and as, moreover, considerable changes in the pro¬ 
portion of forest and of cultivated land, or of dry and wholly 
or partially submerged surface, will often take place within 
brief periods, it is highly desirable that the attention of 
observers, in whose neighborhood the clearing of the soil, or 
the drainage of lakes and swamps, or other great works of 
rural improvement, are going on or meditated, should be espe¬ 
cially drawn not only to revolutions in atmospheric tempera¬ 
ture and precipitation, but to the more easily ascertained and 
perhaps more important local changes produced by these 
operations in the temperature and the hygrometric state of 
the superficial strata of the earth, and in its spontaneous vege¬ 
table and animal products. 
The rapid extension of railroads, which now everywhere 
keeps pace with, and sometimes even precedes, the occupation 
of new soil for agricultural purposes, furnishes great facilities 
for enlarging our knowledge of the topography of the territory 
they traverse, because their cuttings reveal the composition 
and general structure of surface, and the inclination and eleva¬ 
tion of their lines constitute known liypsometrical sections, 
which give numerous points of departure for the measure¬ 
ment of higher and lower stations, and of course for deter¬ 
mining the relief and depression of surface, the slope of the 
beds of watercourses, and many other not less important 
questions.* 
the relative temperatures of hills and valleys to a much greater extent than 
has been usually supposed. A gentleman well known to me kept a ther- 
mometrical record for nearly half a century, in a New England country 
town, at an elevation of at least 1,500 feet above the sea. During these 
years his thermometer never fell lower than 26° Fahrenheit, but at the 
shire town of the county, situated in a basin one thousand feet lower, and 
ten miles distant, as well as at other points in similar positions, the mer¬ 
cury froze several times in the same period. 
* Railroad surveys must be received with great caution where any 
motive exists for cooking them. Capitalists are shy of investments in roads 
with steep grades, and of course it is important to make a fair show of 
facilities in obtaining funds for new routes. Joint-stock companies have 
no souls; their managers, in general, no consciences. Cases can be cited 
